The present invention relates to a circuit arrangement for operating an electrical machine.
A circuit arrangement for activating and deactivating an electrical machine, having an inductive component in which a free-running circuit that is connected in parallel to the electric machine reduces the magnetic energy stored in the inductive component after deactivation, is known from German Patent Application A 42 29 440. The free-running circuit includes a switch, for example a MOSFET, that is activated immediately after deactivation of the output stage. The advantage of using a switch in free-running mode instead of a diode is that less power is lost while current is flowing in the free-running circuit. The active state of the switch positioned in the free-running circuit ends when an activation signal is generated for the electrical machine.
A step-down constant-current transformer, which is equipped with switches operating as synchronous rectifiers to reduce power loss, is known from German Patent Application A 198 41 341. In pulsating mode, a reverse current that flows through the choke from the output in the direction of the input may temporarily occur. To avoid the reverse current flowing through the synchronous rectifier, a device for detecting the current direction is provided to evaluate the voltage drop across the synchronous rectifier.
The object of the present invention is to provide a circuit arrangement for operating electrical machines having an inductive component that makes it possible to optimize efficiency.
The object is achieved by the features specified in the independent claim.